1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device and a method for fabricating the same, and more particularly, to an LCD device for switching between a wide viewing angle display mode and a narrow viewing angle display mode and a method for fabricating the same.
2. Description of the Related Art
For a flat panel display device with a high picture quality and low consumption power, liquid crystal display (LCD) devices are being increasingly used. LCD devices control an optical transmittance using a liquid crystal layer interposed between two substrates and by controlling an intensity of an electric field applied to an electrode formed at the substrate. LCD devices are being widely used in notebook computers, personal digital assistants (PDAs), video telephones, televisions, and various portable electronic devices.
According to a user's various demands, an LCD device having a large screen, a fine pitch, and a wide viewing angle is being developed. LCD devices having a wide viewing angle include an LCD device using a horizontal field driving method, and an LCD device having a compensating film using a vertical alignment (VA) method.
In the LCD device using the horizontal field driving method, a pixel electrode and a common electrode are formed on the same substrate such that an electric field horizontal to the substrate is formed between the pixel electrode and the common electrode when the pixel electrode is turned on. Accordingly, a long axis of liquid crystal molecules is operated in parallel with the substrate according to the pixel electrode being switched on or off. As a result, a refractive index of the liquid crystal observed by the user's eyes is small, thereby providing an excellent contrast ratio and wide viewing angle.
By comparison, an LCD device using the vertical alignment (VA) method implements a viewing angle by attaching a compensation film at an inner side of a polarizing plate. The LCD device using the vertical alignment (VA) method comprises a pair of transparent substrates having a transparent electrode at an inner surface thereof, a liquid crystal material injected between the two substrates and aligned to be perpendicular to the substrate, and a pair of polarizing plates perpendicularly attached to an outer surface of each transparent substrate for polarizing light. Recently, a mode in which liquid crystal molecules are divided by forming an opening pattern or a protrusion on a transparent electrode without performing a rubbing has been proposed.
A general LCD device for implementing a viewing angle will be explained with reference to FIG. 1. FIG. 1 is a sectional view schematically showing a liquid crystal display (LCD) device in accordance with the related art.
As shown, a general LCD device comprises a thin film transistor (TFT) array substrate 11, a color filter substrate 41 facing and attached to the TFT array substrate 11 with a uniform gap, and a liquid crystal layer 51 disposed between the TFT array substrate 11 and the color filter substrate 41. On the TFT array substrate 11, pixels are arranged in a matrix form. A thin film transistor 20, a pixel electrode 27, and a capacitor (not shown) are formed at each unit pixel. The thin film transistor 20 comprises a gate electrode 13 formed on the TFT array substrate 11, a gate insulating layer 15 formed on the TFT array substrate 11 including the gate electrode 13, a semiconductor layer 17, and source/drain electrodes 21 and 23 formed on the semiconductor layer 17 and spaced from each other with a certain gap. The pixel electrode 27 is electrically connected to the drain electrode 23 through a drain contact hole (not shown) formed in a passivation layer 25 formed on an entire surface of the TFT array substrate 11 having the source/drain electrodes 21 and 23. On the color filter substrate 41, a common electrode 47 for applying an electric field through the liquid crystal layer 51 to the pixel electrode 27 of the TFT array substrate 11, R, G, and B color filters 45 for implementing color, and a black matrix 43 are formed. An alignment layer (not shown) is formed at the inside surfaces of the TFT array substrate 11 and the color filter substrate 41. Also, liquid crystal is arranged on a surface of the alignment layer (not shown) in a certain direction determined by a rubbing direction of the alignment layer.
The liquid crystal is rotated by dielectric anisotropy when an electric field is applied between the pixel electrode 27 formed at each pixel of the TFT array substrate 11 and the common electrode 47 formed at the front surface of the color filter substrate 41. Accordingly, images are displayed by passing light through each pixel or by preventing light from being transmitted through each pixel.
The color filter substrate 41 and the TFT array substrate 11 are respectively provided with a first polarizing plate 61 and a second polarizing plate 63. The polarizing plates 61 and 63 polarize natural light incident with vibration in several directions into one direction (that is, polarization).
In the LCD device, light 71 from a backlight is emitted to a front surface of an LCD panel, and the light passes through several diffusion sheets (not shown) to obtain a uniform brightness. As the light is incident on the front surface of the LCD panel, an image can be displayed in a wide viewing angle.
The general LCD device being developed generally has a wide viewing angle. However, in specific cases, the LCD device is desired to have a narrow viewing angle.
The related art LCD device has a number of problems. For example, even if an image can be displayed in a wide viewing angle using light incident on the front surface of the LCD panel, a narrow viewing angle and a wide viewing angle cannot be actively controlled. Although not shown, a viewing angle can be narrowed by applying a film-type filter or an optical fiber to the LCD panel. However, a display mode cannot be switched between a wide viewing angle and a narrow viewing angle, and a brightness of the front surface of the LCD panel is drastically decreased.